The LYMPHATIC System Functions of the Lymphatic System

The LYMPHATIC System

Functions of the Lymphatic System • • • Return fluid from the extracellular spaces to the bloodstream Protects the body from pathogenic microorganisms (defends the body against diseases) “Biological Filtering System”

Homeostasis and the Lymphatic System • • • Supports homeostasis by recycling fluids back into the bloodstream Defends the body against diseases which disrupt homeostasis “Biological Filtering”

The Lymphatic Network • • • The flow of interstitial fluid from the extracellular spaces into the lymphatic network is primarily influenced by a pressure gradient Once within the network the fluid is called lymph. A clear fluid with a high protein concentration. “Second Circulation”

The Lymphatic Network

Structures of the Lymphatic Network • Lymphatic Capillaries – Blind ended vessels where Lymph flow begins – Similar in structure to blood capillaries – Single layer of epithelial tissue • Lymphatic Vessels – Larger continuations of the capillaries that carry Lymph toward the heart – Similar in structure to veins – Contain one-way valves

Lymphatic Capillaries

Movement of Lymph • • • Flows by pressure gradients into lymphatic capillaries and into lymphatic vessels Moves toward the heart by the action of skeletal muscle pumps and respiratory muscle pumps Assisted by one-way valves

Skeletal Muscle Pump

Lymphatic Tissue Organs • • • Lymph Nodes Spleen Thymus Gland Tonsils Red Bone Marrow

Lymph Nodes • • • Small oval masses of lymphoid tissue Composed mainly of lymphocytes Concentrated in the neck, armpit, groin, and abdominal cavity

Lymph Node Structures

Function of Lymph Nodes • • As lymph flows through the nodes, lymphocytes and macrophages removes foreign particles and cleans the fluid Substances removed include: – bacteria – viruses – toxins

Spleen • • Largest organ of the lymphatic system Located on the left side of the abdominal cavity just below the diaphragm Surrounded by a fibrous capsule Internally, consists of white pulp – Lymphocytes - Macrophages • • • Also contains Red Pulp (venous sinuses) Large filter for removing foreign particles and old, worn out cells A major blood reservoir

Spleen

Thymus Gland • • • Soft, bi-lobed structure located in the thoracic cavity (mediastinum) Located above the heart in infants Reduced size in adults Composed of lymphoid tissue Active during times of rapid development of the immune system – 6 months to 5 years of age • In infants - site of T-Lymphocytes (T-Cells) maturation

Thymus Gland

Tonsils • • Located in the mouth and throat 3 pairs – palatine • • - pharyngeal - lingual Composed of lymphoid tissue White blood cells within the tissue destroy pathogens in the mouth and throat regions

Red Bone Marrow • • • Located in the spongy bone tissue Site of hematopoiesis - production of all blood cells including lymphocytes Site of B-Lymphocyte maturation

Immunity • • What is Immunity? Lets ask the expert… Jeff Probst Host- CBS Survivor

Components of Immunity • Antigens - foreign substances that stimulate the immune response – White blood cells recognize these as foreign • Antibodies - proteins produced by cells that react with antigens by binding with them forming an antigen-antibody complex – Belong to a family of proteins known as Immunoglobins (Ig)

The Immune Response • • A response by the body to a specific foreign substance or invader Two Types of Response Mechanisms Cell Mediated Immunity - cells phagocytize the invading pathogen Antibody Mediated (Humoral) Immunity - antibodies of the body attack and destroy the invader

Lymphocytes • • White blood cells involved in the immune response Development and Maturation – Originate in the red bone marrow – Mature in the thymus gland (T-Cells) – Mature in the bone marrow and Peyer’s patches (B -Cells) • Immunocompetence – The programming of lymphocytes to distinguish and identify cells as either self or non-self cells

T-Cells • • • Undergoes development in the thymus gland then migrates to the lymphoid tissue Once in lymphoid tissue, binds to specific antigens and develop into different cell lines Different T-Cell Lines: – Killer T-Cells - Helper T-Cells – Suppressor T-Cells - Memory T-Cells

B Cells • • Undergo development in the red bone marrow or Peyer’s patches and then migrate to the lymphoid tissue Once they bind to an antigen they develop into one of two different cell lines Plasma Cells - synthesize and release antibodies Memory B-Cells - stores information about the specific antigen for the next encounter

Acquired Immunity • • The ability to develop immunity after initial exposure to a particular type of antigen 4 different mechanisms of developing immunity. – – Naturally Acquired Active Immunity Naturally Acquired Passive Immunity Artificially Acquired Active Immunity Artificially Acquired Passive Immunity

Naturally Acquired Active Immunity • • Immunity as a result of previous exposure to pathogens under natural conditions Examples: – measles – chicken pox – influenza

Naturally Acquired Passive Immunity • • Immunity caused by the transfer of antibodies from one person to another Transfer of antibodies from a mother to infant during fetal development Transfer of antibodies from mother to infant during breast feeding Examples: – polio - rubella - diphtheria

Artificially Acquired Passive Immunity • • immunity induced by the introduction of antibodies from an animal or another person antibodies are injected in an active state and therefore provide protection against disease causing agents immediately – snake anti-venoms – hepatitis • - rabies - tetanus very effective but very short lived

Artificially Acquired Active Immunity • • immunity acquired by artificial introduction of a vaccine administered by injection or orally – diphtheria – measles • - pertussis (DPT) - rubella (MMR) may be long lasting or lifelong – measles • - tetanus - mumps - polio preferred method of stimulating the immune response

Immunization The ability of the immune system to respond activate the immune response quickly during repeated exposure to infectious disease.

Vaccine • • A suspension of parts of microorganisms, inactivated whole microorganisms, or inactivated toxins Administered to induce an immune response When later exposed to the active form of the disease, the individual already has the antibodies to fight against it Common Vaccines: – chicken pox – mumps - hepatitis A/B - polio -flu - measles - tetanus

AIDS Acquired Immunodeficiency Syndrome • A disease caused by a virus (HIV) – Human Immunodeficiency Virus • • • Destroys T-Cells (Helper) Results in fatal immunodeficiency Victim dies from infection by another opportunistic disease – pneumonia – dementia - Kaposi’s sarcoma - AIDS Wasting Syndrome

AIDS (Cont. ) • Difference between HIV+ and AIDS – T-Cell count below 200 • normally 800 - 1500 – Two or more opportunistic diseases present • Once diagnosed with AIDS, death usually occurs within 2 - 3 years – This is changing rapidly due to improved drug therapies and lifestyle modifications once diagnosed with the disease

Measles • • A highly communicable disease characterized by fever, general malaise, sneezing, nasal congestion, brassy cough, conjunctivitis, spots on the buccal mucosa, and maculopapular eruptions over the entire body Caused by the Rubeola virus

Mumps • • An acute, contagious, febrile disease characterized by inflammation of the parotid and other salivary glands. Greatest complication -- infertility

Rubella • • An acute infectious disease resembling both scarlet fever and measles but differing from them in that it has a short course, slight fever, and is free from sequelae. Also known as German Measles

Tetanus • An acute infectious disease due to the toxin Clostridium Tetani growing anaerobically at the site of the injury. May cause lockjaw and muscle paralysis.